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1507f512 MR |
1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* | |
3 | * Copyright IBM Corporation, 2021 | |
4 | * | |
5 | * Author: Mike Rapoport <rppt@linux.ibm.com> | |
6 | */ | |
7 | ||
8 | #include <linux/mm.h> | |
9 | #include <linux/fs.h> | |
10 | #include <linux/swap.h> | |
11 | #include <linux/mount.h> | |
12 | #include <linux/memfd.h> | |
13 | #include <linux/bitops.h> | |
14 | #include <linux/printk.h> | |
15 | #include <linux/pagemap.h> | |
16 | #include <linux/syscalls.h> | |
17 | #include <linux/pseudo_fs.h> | |
18 | #include <linux/secretmem.h> | |
19 | #include <linux/set_memory.h> | |
20 | #include <linux/sched/signal.h> | |
21 | ||
22 | #include <uapi/linux/magic.h> | |
23 | ||
24 | #include <asm/tlbflush.h> | |
25 | ||
26 | #include "internal.h" | |
27 | ||
28 | #undef pr_fmt | |
29 | #define pr_fmt(fmt) "secretmem: " fmt | |
30 | ||
31 | /* | |
32 | * Define mode and flag masks to allow validation of the system call | |
33 | * parameters. | |
34 | */ | |
35 | #define SECRETMEM_MODE_MASK (0x0) | |
36 | #define SECRETMEM_FLAGS_MASK SECRETMEM_MODE_MASK | |
37 | ||
38 | static bool secretmem_enable __ro_after_init; | |
39 | module_param_named(enable, secretmem_enable, bool, 0400); | |
40 | MODULE_PARM_DESC(secretmem_enable, | |
41 | "Enable secretmem and memfd_secret(2) system call"); | |
42 | ||
9a436f8f MR |
43 | static atomic_t secretmem_users; |
44 | ||
45 | bool secretmem_active(void) | |
46 | { | |
47 | return !!atomic_read(&secretmem_users); | |
48 | } | |
49 | ||
1507f512 MR |
50 | static vm_fault_t secretmem_fault(struct vm_fault *vmf) |
51 | { | |
52 | struct address_space *mapping = vmf->vma->vm_file->f_mapping; | |
53 | struct inode *inode = file_inode(vmf->vma->vm_file); | |
54 | pgoff_t offset = vmf->pgoff; | |
55 | gfp_t gfp = vmf->gfp_mask; | |
56 | unsigned long addr; | |
57 | struct page *page; | |
58 | int err; | |
59 | ||
60 | if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode)) | |
61 | return vmf_error(-EINVAL); | |
62 | ||
63 | retry: | |
64 | page = find_lock_page(mapping, offset); | |
65 | if (!page) { | |
66 | page = alloc_page(gfp | __GFP_ZERO); | |
67 | if (!page) | |
68 | return VM_FAULT_OOM; | |
69 | ||
70 | err = set_direct_map_invalid_noflush(page); | |
71 | if (err) { | |
72 | put_page(page); | |
73 | return vmf_error(err); | |
74 | } | |
75 | ||
76 | __SetPageUptodate(page); | |
77 | err = add_to_page_cache_lru(page, mapping, offset, gfp); | |
78 | if (unlikely(err)) { | |
79 | put_page(page); | |
80 | /* | |
81 | * If a split of large page was required, it | |
82 | * already happened when we marked the page invalid | |
83 | * which guarantees that this call won't fail | |
84 | */ | |
85 | set_direct_map_default_noflush(page); | |
86 | if (err == -EEXIST) | |
87 | goto retry; | |
88 | ||
89 | return vmf_error(err); | |
90 | } | |
91 | ||
92 | addr = (unsigned long)page_address(page); | |
93 | flush_tlb_kernel_range(addr, addr + PAGE_SIZE); | |
94 | } | |
95 | ||
96 | vmf->page = page; | |
97 | return VM_FAULT_LOCKED; | |
98 | } | |
99 | ||
100 | static const struct vm_operations_struct secretmem_vm_ops = { | |
101 | .fault = secretmem_fault, | |
102 | }; | |
103 | ||
9a436f8f MR |
104 | static int secretmem_release(struct inode *inode, struct file *file) |
105 | { | |
106 | atomic_dec(&secretmem_users); | |
107 | return 0; | |
108 | } | |
109 | ||
1507f512 MR |
110 | static int secretmem_mmap(struct file *file, struct vm_area_struct *vma) |
111 | { | |
112 | unsigned long len = vma->vm_end - vma->vm_start; | |
113 | ||
114 | if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0) | |
115 | return -EINVAL; | |
116 | ||
117 | if (mlock_future_check(vma->vm_mm, vma->vm_flags | VM_LOCKED, len)) | |
118 | return -EAGAIN; | |
119 | ||
120 | vma->vm_flags |= VM_LOCKED | VM_DONTDUMP; | |
121 | vma->vm_ops = &secretmem_vm_ops; | |
122 | ||
123 | return 0; | |
124 | } | |
125 | ||
126 | bool vma_is_secretmem(struct vm_area_struct *vma) | |
127 | { | |
128 | return vma->vm_ops == &secretmem_vm_ops; | |
129 | } | |
130 | ||
131 | static const struct file_operations secretmem_fops = { | |
9a436f8f | 132 | .release = secretmem_release, |
1507f512 MR |
133 | .mmap = secretmem_mmap, |
134 | }; | |
135 | ||
136 | static bool secretmem_isolate_page(struct page *page, isolate_mode_t mode) | |
137 | { | |
138 | return false; | |
139 | } | |
140 | ||
141 | static int secretmem_migratepage(struct address_space *mapping, | |
142 | struct page *newpage, struct page *page, | |
143 | enum migrate_mode mode) | |
144 | { | |
145 | return -EBUSY; | |
146 | } | |
147 | ||
148 | static void secretmem_freepage(struct page *page) | |
149 | { | |
150 | set_direct_map_default_noflush(page); | |
151 | clear_highpage(page); | |
152 | } | |
153 | ||
154 | const struct address_space_operations secretmem_aops = { | |
155 | .freepage = secretmem_freepage, | |
156 | .migratepage = secretmem_migratepage, | |
157 | .isolate_page = secretmem_isolate_page, | |
158 | }; | |
159 | ||
160 | static struct vfsmount *secretmem_mnt; | |
161 | ||
162 | static struct file *secretmem_file_create(unsigned long flags) | |
163 | { | |
164 | struct file *file = ERR_PTR(-ENOMEM); | |
165 | struct inode *inode; | |
166 | ||
167 | inode = alloc_anon_inode(secretmem_mnt->mnt_sb); | |
168 | if (IS_ERR(inode)) | |
169 | return ERR_CAST(inode); | |
170 | ||
171 | file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem", | |
172 | O_RDWR, &secretmem_fops); | |
173 | if (IS_ERR(file)) | |
174 | goto err_free_inode; | |
175 | ||
176 | mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); | |
177 | mapping_set_unevictable(inode->i_mapping); | |
178 | ||
179 | inode->i_mapping->a_ops = &secretmem_aops; | |
180 | ||
181 | /* pretend we are a normal file with zero size */ | |
182 | inode->i_mode |= S_IFREG; | |
183 | inode->i_size = 0; | |
184 | ||
185 | return file; | |
186 | ||
187 | err_free_inode: | |
188 | iput(inode); | |
189 | return file; | |
190 | } | |
191 | ||
192 | SYSCALL_DEFINE1(memfd_secret, unsigned int, flags) | |
193 | { | |
194 | struct file *file; | |
195 | int fd, err; | |
196 | ||
197 | /* make sure local flags do not confict with global fcntl.h */ | |
198 | BUILD_BUG_ON(SECRETMEM_FLAGS_MASK & O_CLOEXEC); | |
199 | ||
200 | if (!secretmem_enable) | |
201 | return -ENOSYS; | |
202 | ||
203 | if (flags & ~(SECRETMEM_FLAGS_MASK | O_CLOEXEC)) | |
204 | return -EINVAL; | |
205 | ||
206 | fd = get_unused_fd_flags(flags & O_CLOEXEC); | |
207 | if (fd < 0) | |
208 | return fd; | |
209 | ||
210 | file = secretmem_file_create(flags); | |
211 | if (IS_ERR(file)) { | |
212 | err = PTR_ERR(file); | |
213 | goto err_put_fd; | |
214 | } | |
215 | ||
216 | file->f_flags |= O_LARGEFILE; | |
217 | ||
218 | fd_install(fd, file); | |
9a436f8f | 219 | atomic_inc(&secretmem_users); |
1507f512 MR |
220 | return fd; |
221 | ||
222 | err_put_fd: | |
223 | put_unused_fd(fd); | |
224 | return err; | |
225 | } | |
226 | ||
227 | static int secretmem_init_fs_context(struct fs_context *fc) | |
228 | { | |
229 | return init_pseudo(fc, SECRETMEM_MAGIC) ? 0 : -ENOMEM; | |
230 | } | |
231 | ||
232 | static struct file_system_type secretmem_fs = { | |
233 | .name = "secretmem", | |
234 | .init_fs_context = secretmem_init_fs_context, | |
235 | .kill_sb = kill_anon_super, | |
236 | }; | |
237 | ||
238 | static int secretmem_init(void) | |
239 | { | |
240 | int ret = 0; | |
241 | ||
242 | if (!secretmem_enable) | |
243 | return ret; | |
244 | ||
245 | secretmem_mnt = kern_mount(&secretmem_fs); | |
246 | if (IS_ERR(secretmem_mnt)) | |
247 | ret = PTR_ERR(secretmem_mnt); | |
248 | ||
249 | /* prevent secretmem mappings from ever getting PROT_EXEC */ | |
250 | secretmem_mnt->mnt_flags |= MNT_NOEXEC; | |
251 | ||
252 | return ret; | |
253 | } | |
254 | fs_initcall(secretmem_init); |